This invention relates to exhaust gas recirculation (EGR) valves for internal combustion engines, and is particularly directed to a novel construction for integrating a position sensor with an electric actuator in such a valve.
Controlled engine exhaust gas recirculation is a known technique for reducing oxides of nitrogen in products of combustion that are exhausted from an internal combustion engine to atmosphere. A typical EGR system comprises an EGR valve that is controlled in accordance with engine operating conditions to regulate the amount of engine exhaust gas that is recirculated to the induction fuel-air flow entering the engine for combustion so as to limit the combustion temperature and hence reduce the formation of oxides of nitrogen.
Because they are typically engine-mounted, EGR valves are subject to harsh operating environments that include wide temperature extremes and vibrations. Tailpipe emission requirements impose more stringent demands for improved control of such valves. An electric actuator, such as a solenoid, is one device for obtaining improved control. Further control improvement can be obtained by associating a position sensor with the electric actuator to sense the position to which the valve is being opened by the actuator, and by using position feedback to control the electric current that operates the actuator. Such an actuator and position sensor must be able to operate properly in such extreme environments for extended periods of use.
A known construction for an EGR valve that comprises an electric actuator and associated position sensor also has a single electric connector for mating which a complementary connector of a wiring harness in a motor vehicle to make electric circuit connections of both actuator and position sensor to an electric control circuit that operates the valve. That connector may be part of the position sensor housing. Terminations of the wire forming the electric actuator must be soldered, or in some way joined, to corresponding electric terminals that are part of the connector.
It is believed that improvements provided by the present invention may avoid possible failures modes that could occur in an EGR valve having the construction just described, thereby making an EGR valve less prone to failure. The improvements arise by better integration of the position sensor with the actuator.
Moreover, in mass-production automotive vehicle applications, component cost-effectiveness is important. An EGR valve electric actuator and associated position sensor that possess an arguably more rugged construction and a capability for improved control is believed desirable for use in a vehicle having an internal combustion engine that is equipped with an EGR system.
The present invention relates to new and unique construction for an EGR valve, particularly a construction in which a position sensor is integrated with an electric actuator in new and improved ways.
A general aspect of the invention relates to an exhaust gas recirculation valve for an internal combustion engine comprising an inlet port at which exhaust gas enters the valve, an outlet port at which exhaust gas exits the valve, and a valve element for selectively restricting exhaust gas flow between the inlet port and the outlet port. An electric actuator comprises an electromagnet coil disposed on a non-metallic bobbin having a flange bounding one end of the coil. An armature forms a portion of a magnetic circuit that is operated by the coil for selectively positioning the valve element. A position sensor provides an electric signal of armature position. The magnetic circuit further comprises a stator member having a flange disposed against the flange of the bobbin, and the position sensor further comprising a non-metallic housing having a base that captures the stator member flange against the bobbin flange. The stator member flange comprises apertures through which non-metallic material that joins with the bobbin flange passes to join with the position sensor housing base to thereby unite the bobbin and the position sensor housing in assembly capturing the stator member flange.
Another general aspect relates to a method of making the valve by capturing the stator member flange between the bobbin flange and the housing base, and then joining the bobbin flange and the housing base through the stator member flange apertures by a material melting process.
Still another general aspect relates to a method of making the valve by disposing the stator member in a mold cavity, and injecting non-metallic material into the cavity to create the bobbin and the position sensor housing, including causing the injected non-metallic material to pass through the apertures in the stator member flange, and allowing the injected material to cure to cause the stator member flange to be captured between the bobbin flange and the housing base, and the bobbin flange and the housing base to be integrally joined through the stator member flange apertures by cured injected material.
Still another general aspect relates to an exhaust gas recirculation valve for an internal combustion engine comprising an inlet port at which exhaust gas enters the valve, an outlet port at which exhaust gas exits the valve, and a valve element for selectively restricting exhaust gas flow between the inlet port and the outlet port. An electric actuator comprises an electromagnet coil disposed on a polymeric bobbin having a flange bounding one end of the coil. An armature forms a portion of a magnetic circuit that is operated by the coil for selectively positioning the valve element. A position sensor provides an electric signal of armature position. The magnetic circuit further comprises a stator member having a flange disposed against the flange of the bobbin, and the position sensor further comprises a housing having a polymeric base that captures the stator member flange against the bobbin flange. The stator member flange comprises apertures through which polymeric material integrally joins the bobbin flange and the position sensor housing base in assembly.
The accompanying drawings, which are incorporated herein and constitute part of this specification, include one or more presently preferred embodiments of the invention, and together with a general description given above and a detailed description given below, serve to disclose principles of the invention in accordance with a best mode contemplated for carrying out the invention.